4 Bit Lcd Hookup

[mister_e]

I have been running an lcd on portc of a 16F877A, (4 bit mode). I need the SPI functions of portc for a DAC. Where can I put the lcd? Porta is needed for other uses. Does lcd need a clock input to the Ebit?

why not using Shiftin/Shiftout who give you the choice to choose those pin you want?

The Edward suggestion is also good if you don't need any pins for PWM or interrupts.

LCDOUT and SHIFTIN/SHIFTOUT don't use any internal ressource, software based only.

[GEEZER]

Thanks Edward, the LCD must operate whether the serial DAC is operating or not. My LCD and my serial operated DAC must be totally autonomous.

I saw a post recently where a guy was running three serial ports out of one chip, so I am sure there is some way to run the LCD and still have one serial output.

Steve, correct me if I'm wrong. The shift out command looks to be a one bite at a time affair with a lot of code.

I could get a parallel operated DAC, but wouldn't I still need a clocking pin?

Your suggestions are greatly appreciated.

The Geezer

[mister_e]

wich DAC you want to use? If i can suggest one simple MAX517 wich work with the I2C bus. Yeah ok, only 8 bit of definition but, how much precision do you need?

[GEEZER]

The DAC is an adXXXXX, can't rember the exact number. It's a quad with 255 steps per channel. 8 data bits and 2 bits to select channel. It requires an SPI output, an sdo, a clock pin and a ground, I believe. These are available on portC.

I think I can work that all out, but I need to move the LCD from portc, where it is working fine, to leave those aformentioned portc pins for the DAC.

I am not asking someone to write my code, I am willing to do the work. To make my question more clear:

I understand that pins 7,6,5, & 4, on portb will transfer the data or commands in two 4 bit parts. I understand that the RS signal will tell the LCD chip whether the transfered data is a command such as clear-screen, or data to be displayed such as "Hello".

I am ASSUMING that the E_BIT is a timing pin which drives the whole shbang much like an oscillatior.

I am ASSUMING that the LCDOUT command is not just a word, but a binary routine, ( when compiled) that controls these involved pins, and in a timed sequence send commands followed by data to control the Hitachi chip and make it do what my basic program code tells it.

I can use a clko pin from portc and make all this work. But I need another pin for this function, because I need the portc hardware to run my SPI DAC.

Does this make sense? I am confident there is some quite simple way to do it. My novice status (read ignorance), is my drawback. If you can help me with an understanding of theory, I know I can work it out.

You will notice In the above paragraphs I use the word "understand", (read "think I understand"), and "ASSUMING" which best describes the user of the word with the first 3 letters of the word.

Any assistance is greatly appreciated.

The Geezer

[GEEZER]

Thanks everyone. I am running on portb now, with EBIT and RS on portc. Have pins left on C for my serial hookup DAC.

Thanks much,

The Geezer

P.S. And as Arnold says, "I'll be back".